/** * Copyright (c) 2016-present, RxJava Contributors. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in * compliance with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software distributed under the License is * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See * the License for the specific language governing permissions and limitations under the License. */ package io.reactivex.subjects; import java.util.concurrent.atomic.*; import io.reactivex.*; import io.reactivex.annotations.*; import io.reactivex.disposables.Disposable; import io.reactivex.plugins.RxJavaPlugins; /** * Represents a hot Single-like source and consumer of events similar to Subjects. * <p> * All methods are thread safe. Calling onSuccess multiple * times has no effect. Calling onError multiple times relays the Throwable to * the RxJavaPlugins' error handler. * <p> * The SingleSubject doesn't store the Disposables coming through onSubscribe but * disposes them once the other onXXX methods were called (terminal state reached). * <p>History: 2.0.5 - experimental * @param <T> the value type received and emitted * @since 2.1 */ public final class SingleSubject<T> extends Single<T> implements SingleObserver<T> { final AtomicReference<SingleDisposable<T>[]> observers; @SuppressWarnings("rawtypes") static final SingleDisposable[] EMPTY = new SingleDisposable[0]; @SuppressWarnings("rawtypes") static final SingleDisposable[] TERMINATED = new SingleDisposable[0]; final AtomicBoolean once; T value; Throwable error; /** * Creates a fresh SingleSubject. * @param <T> the value type received and emitted * @return the new SingleSubject instance */ @CheckReturnValue @NonNull public static <T> SingleSubject<T> create() { return new SingleSubject<T>(); } @SuppressWarnings("unchecked") SingleSubject() { once = new AtomicBoolean(); observers = new AtomicReference<SingleDisposable<T>[]>(EMPTY); } @Override public void onSubscribe(@NonNull Disposable d) { if (observers.get() == TERMINATED) { d.dispose(); } } @SuppressWarnings("unchecked") @Override public void onSuccess(@NonNull T value) { if (value == null) { onError(new NullPointerException("Null values are not allowed in 2.x")); return; } if (once.compareAndSet(false, true)) { this.value = value; for (SingleDisposable<T> md : observers.getAndSet(TERMINATED)) { md.actual.onSuccess(value); } } } @SuppressWarnings("unchecked") @Override public void onError(@NonNull Throwable e) { if (e == null) { e = new NullPointerException("Null errors are not allowed in 2.x"); } if (once.compareAndSet(false, true)) { this.error = e; for (SingleDisposable<T> md : observers.getAndSet(TERMINATED)) { md.actual.onError(e); } } else { RxJavaPlugins.onError(e); } } @Override protected void subscribeActual(@NonNull SingleObserver<? super T> observer) { SingleDisposable<T> md = new SingleDisposable<T>(observer, this); observer.onSubscribe(md); if (add(md)) { if (md.isDisposed()) { remove(md); } } else { Throwable ex = error; if (ex != null) { observer.onError(ex); } else { observer.onSuccess(value); } } } boolean add(@NonNull SingleDisposable<T> inner) { for (;;) { SingleDisposable<T>[] a = observers.get(); if (a == TERMINATED) { return false; } int n = a.length; @SuppressWarnings("unchecked") SingleDisposable<T>[] b = new SingleDisposable[n + 1]; System.arraycopy(a, 0, b, 0, n); b[n] = inner; if (observers.compareAndSet(a, b)) { return true; } } } @SuppressWarnings("unchecked") void remove(@NonNull SingleDisposable<T> inner) { for (;;) { SingleDisposable<T>[] a = observers.get(); int n = a.length; if (n == 0) { return; } int j = -1; for (int i = 0; i < n; i++) { if (a[i] == inner) { j = i; break; } } if (j < 0) { return; } SingleDisposable<T>[] b; if (n == 1) { b = EMPTY; } else { b = new SingleDisposable[n - 1]; System.arraycopy(a, 0, b, 0, j); System.arraycopy(a, j + 1, b, j, n - j - 1); } if (observers.compareAndSet(a, b)) { return; } } } /** * Returns the success value if this SingleSubject was terminated with a success value. * @return the success value or null */ @Nullable public T getValue() { if (observers.get() == TERMINATED) { return value; } return null; } /** * Returns true if this SingleSubject was terminated with a success value. * @return true if this SingleSubject was terminated with a success value */ public boolean hasValue() { return observers.get() == TERMINATED && value != null; } /** * Returns the terminal error if this SingleSubject has been terminated with an error, null otherwise. * @return the terminal error or null if not terminated or not with an error */ @Nullable public Throwable getThrowable() { if (observers.get() == TERMINATED) { return error; } return null; } /** * Returns true if this SingleSubject has been terminated with an error. * @return true if this SingleSubject has been terminated with an error */ public boolean hasThrowable() { return observers.get() == TERMINATED && error != null; } /** * Returns true if this SingleSubject has observers. * @return true if this SingleSubject has observers */ public boolean hasObservers() { return observers.get().length != 0; } /** * Returns the number of current observers. * @return the number of current observers */ /* test */ int observerCount() { return observers.get().length; } static final class SingleDisposable<T> extends AtomicReference<SingleSubject<T>> implements Disposable { private static final long serialVersionUID = -7650903191002190468L; final SingleObserver<? super T> actual; SingleDisposable(SingleObserver<? super T> actual, SingleSubject<T> parent) { this.actual = actual; lazySet(parent); } @Override public void dispose() { SingleSubject<T> parent = getAndSet(null); if (parent != null) { parent.remove(this); } } @Override public boolean isDisposed() { return get() == null; } } }